WARNING: This plugin doesn't currently work. Feel free to download it and
figure out what's wrong. The current bugs are:

It does not send out new comment/moderation notifications at all.

It sends out one copy of notifications generated by the Subscribe to Comments
plugin for each person subscribed. (Fixed in trunk)

Mail Manager adds a plethora of new email notification options to WordPress
for multiuser blogs. Instead of notifying the blog administrator or post
author of all administrative activity, you can define who gets notified of
what events, allowing for specific users to handle different administrative
activities on a multiuser blog.

Notification options include:

New comments and comments awaiting moderation

Changes in post or page status (e.g. pending review) (future)

Changes in user status (future)

Mail Manager is compatible with WordPress 2.0 and later and WordPress MU
1.0 and later.

Mail Manager is pre-release software and is missing planned features, and
almost certainly has bugs. Please report any bugs you may find.